Activation of c-Src and Fyn kinases by protein-tyrosine phosphatase RPTPalpha is substrate-specific and compatible with lipid raft localization.
Src family tyrosine kinases (SFKs) function in multiple signaling pathways, raising the question of how appropriate regulation and substrate choice are achieved. SFK activity is modulated by several protein-tyrosine phosphatases, among which RPTPalpha and SHP2 are the best established. We studied how RPTPalpha affects substrate specificity and regulation of c-Src and Fyn in response to epidermal growth factor and platelet-derived growth factor. We find that RPTPalpha, in a growth factor-specific manner, directs the specificity of these kinases toward a specific subset of SFK substrates, particularly the focal adhesion protein Paxillin and the lipid raft scaffolding protein Cbp/PAG. A significant fraction of RPTPalpha is present in lipid rafts, where its targets Fyn and Cbp/PAG reside, and growth factor-mediated SFK activation within this compartment is strictly dependent on RPTPalpha. Forced concentration of RPTPalpha into lipid rafts is compatible with activation of Fyn. Finally, RPTPalpha-induced phosphorylation of Paxillin and Cbp/PAG induces recruitment of the SFK inhibitory kinase Csk, indicative of negative feedback loops limiting SFK activation by RPTPalpha. Our findings indicate that individual SFK-controlling PTPs play important and specific roles in dictating SFK substrate specificity and regulatory mechanism.
Vacaresse
Nathalie
N
Biotech Research and Innovation Center, Copenhagen Biocenter, Ole Maaløes Vej 5, 2200 Copenhagen N, Denmark.
Møller
Bente
B
Danielsen
E Michael
EM
Okada
Masato
M
Sap
Jan
J
D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation / Q000187:drug effects / Q000502:physiology; D004815:Epidermal Growth Factor / Q000494:pharmacology; D016391:Genes, src / Q000502:physiology*; D036341:Intercellular Signaling Peptides and Proteins; D021962:Membrane Microdomains / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D051419:Paxillin / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11 / Q000235:genetics / Q000378:metabolism; D051076:Proto-Oncogene Proteins c-fyn / Q000235:genetics / Q000378:metabolism*; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4 / Q000235:genetics / Q000378:metabolism*; D013379:Substrate Specificity / Q000187:drug effects / Q000502:physiology
D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; C408344:Pag protein, mouse; D051419:Paxillin; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; C496062:Pxn protein, mouse; D004815:Epidermal Growth Factor; C494960:Fyn protein, mouse; D051076:Proto-Oncogene Proteins c-fyn; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; C516725:Ptpn11 protein, mouse; C516843:Ptpra protein, mouse; D054630:Receptor-Like Protein Tyrosine Phosphatases, Class 4